There is no usual encounter. No two massage experiences, even with the same masseur, are necessarily the same. Some guys never drop their shorts and won't let you fondle them, others get naked at the start or at least while you're still face down and are open to being fondled or more, some much more. Some guys will make a point of letting their junk find your hand while they're working on your back. A few will even spend a considerable time standing at your head to see if you show an interest in fondling them with your mouth, hehe. Unless the guy more or less puts his cock in my hand, I tend to leave the masseur alone while I'm face down so that he can concentrate on the massage, which is what I prefer.
Once you flip over, odds are high--but not 100%--that he'll be naked and your own interest in more than the massage will be showing. After that, experiences vary tremendously, from an almost detached HE, to something more sensous and erotic, sometimes while you stroke him, to complete mutual JO, to full on 69, or even to his straddling you and ride 'em cowboy. On the other hand, some guys won't let any oral happen, and some won't even let you fondle them much less go beyond that. You need to gently show your interest, and let him respond, or it might involve responding to him. They're usually clear about whatever their own personal limits are. A couple of times, even after all was done, the kiss goodbye got us both heated up again and we ended up on his bed, so you never know. YMMV is definitely the way to describe it.
I have very little experience with upselling since I studiously avoid the guys who are reported here to have that practice. Maybe others can chime in.
If you can find guys here who've been to the masseur you're considering, you can usually get a pretty good idea of how that masseur works, but there are some masseurs whose limits will vary depending on how they react to you. Sometimes the hottest customers get a lot more service than the rest of us. And who's hot will be relative to that masseur's personal taste. That's life.